Research On Microwave Biosensor Based On Integrated Passive Device Manufacturing Process

In today’s world,there are several diseases that require early detection and immediate medical assistance.Referring to serious medical problems,the point of care testing(POCT)technique with fast diagnosis and early detection of a disease is highly in demand.Several biosensors have been introduced by biomedical researchers that are perfectly matched with the above requirements.Among all existed biosensors,microwave-based biosensors have been considered a promising candidate for POCT applications.However,the existing microwave biosensors are restricted to achieve high accuracy,low detection limit,excellent sensitivity,reproducibility,and minimum cost.Hence,the anticipated microwave biosensor has been introduced to fetch the benefits to bear in novel and unanticipated applications.The microwavebased sensors offer numerous advantages,but the large structural dimensions at low frequency are still a serious challenge.There are different biosensors available in the market for sensing applications,such as optical biosensors,electrochemical biosensors,field-effect transistor type biosensors,and microwave sensors.Each biosensing principle has its own disadvantages,which restrict them to use as an ideal biosensor for POCT applications.The POCT technique requires a biosensor that could perform continuous monitoring,fast diagnosis,and early detection.These requirements could be fulfilled by microwave sensors.Additionally,microwave sensors operate at communication frequencies,which allow them to use for wireless broadcast and remote sensing applications.The microwave-based sensing also includes second-order conductimetric transduction,which offers multi-parametric data investigation for enhancing the selectivity of the microwave sensors.The multi-parametric data analysis uncovers the hidden physicochemical properties of the analyte.Therefore it is essential to explore the microwave sensor in terms of high-frequency conductivity and dielectric property.The literature review exhibited that microwave sensors are suitable for sensing applications,but a large size at low frequencies restricts them to use in POCT applications.Though,integrated passive device(IPD)technology has been recently introduced to overcome the problems of large dimensions by miniaturizing the microwave device dimension from cm to μm with a cost-effective approach.To design a miniaturized microwave device,the understanding of the IPD technique is essential to design a cost-effective,low-loss,error-free,and miniaturized microwave device.However,the IPD architecture mainly comprises of resistors(R),inductors(L),and capacitors(C),which can be used as building blocks for RF and microwave structures and easily resembled with all microstrip-based microwave devices.The understanding of mathematical modeling and theoretical explanation towards lumped element devices are prime requirements to fabricate a device with minimum errors.However,the empirical expressions are not enough to precisely forecast the lumped element results.Hence computational algorithms and user-friendly 3-D simulator applications should be used to develop R,L,and C components.In addition to the usage of mathematical modeling,the proper design steps,and precise fabrication process is profoundly required to design low-cost,error-free,and miniaturized microwave devices through IPD technology.Based on the precise manufacturing process of IPD technology developed by the proposed thesis,a miniaturized microwave resonator is designed.The mathematical modeling,3-D simulation results,and fabrication device measurement results prove that the proposed resonator has low loss and high precision characteristics at a specific resonating frequency.Afterward,a microminiaturized,as well as highly integrated micro/nano processing technology is used to design a high consistent,low loss,and error-free microwave biosensor for glucose sensing application.The proposed LC-type microwave resonator is constructed to overcome the drawbacks of enhanced Q-factor and high penetration depth in IPD based microwave sensors.The multi-layer entangled air-bridge-based asymmetrical differential spiral inductor has been designed to achieve an enhanced Q-factor.Moreover,the entangled air-bridgebased asymmetrical differential spiral inductor and the circular finger-based inter-digital capacitor are optimized to attain high inductance and capacitance with low resonating frequency(1.5 GHz),which is responsible for high penetration depth.The high penetration depth enhances the interaction of electromagnetic waves with the deposited sample ions over a broader region.Additionally,the mathematical analysis in the designed microwave sensor is illustrated to observe the approximation of the complex effective permittivity value as per frequencydependent glucose sample.Furthermore,the temperature effect on glucose-sensing is analyzed to check the suitability of real-time blood glucose measurement in an open environment,which is a prime requirement for POCT application.Furthermore,after the successful implementation of the glucose-based microwave sensor,the improved version of the LC-type microwave resonator is optimized to attain enhanced quality factor,excellent filling factor,and high penetration depth,which is suitable to achieve high sensitivity during dopamine,uric acid,and ascorbic acid detection.The square spiral capacitor offers intensified electric field intensity compared with interdigital capacitors,which is a responsible factor in achieving a high filling factor.The induction of high electric field intensity and low resonating frequency is due to the presence of an elongated span circularshaped conductive path in the square spiral capacitor.Furthermore,the feeding ports of the IPDtype biosensor have been fully covered with a special polymer gel,which prevents the damage of feedline connection and responsible for multiple sensing measurements using a single device.The single LC-type microwave resonator is used to sense multiple samples of dopamine,uric acid,and ascorbic acid(each biochemical is isolated into six different concentrations,and each sample concentration is tested five times),which reflects that the proposed design can perform high repeatability detection.The fruitful outcome of the proposed microwave sensor indicates that IPD-based microwave sensors are suitable for real-time detection,which is ideal for POCT applications.